Updated 'comments callback' location comment

The function has been moved outside of 'functions.php' and into 'inc/template-tags.php'. This directs developers to the proper location for the callback.
Merge pull request #156 from inspectorfegter/patch-1

Updated 'comments callback' location comment
Change apos back to the correct rsquo. See #84.
Merge remote-tracking branch 'upstream/master'